Tiny robot fish developed to collect microplastics

Microplastics are the breakdown products of plastic objects that we use in everyday life – wrappers, wrappers, bottles, synthetic clothing and kitchen utensils, for example. None of these plastics are biodegradable, but in the presence of sunlight and normal environmental conditions, they perish into small fragments that end up in oceans, rivers, food, drinking water and even human blood. humans and others animals. They are one of the biggest environmental problems in the world because, once dispersed, they are very difficult to eliminate.

Scientists have previously proposed the use of soft robots to collect these microscopic plastic particles, but soft robots are typically made of hydrogels or silicone rubber, which are mechanically inferior and easily damaged in ocean conditions. In a new study published by the American chemical society in the review Nano-lettersChinese and German scientists have used nanotechnology to develop a light-activated robot fish made of composite sheets of graphene that can quickly “swim” and remove microplastics from the environment.

“It is very important to develop a robot to accurately collect and sample harmful microplastic pollutants from the aquatic environment,” said Yuyan Wang, a researcher at the Polymer Research Institute of Sichuan University and one of the lead authors of the study. “To our knowledge, this is the first example of such soft robots.”

The experts used a substance called mother-of-pearl, also known as mother-of-pearl, on which to base the design of a new material. Mother of pearl is strong and flexible and is found on the inner surfaces of clam shells. Nacre layers have a microscopic gradient, going from one side with lots of calcium carbonate to the other side with mostly silk protein filler. Inspired by this substance, Xinxing Zhang, also from Sichuan University’s Polymer Research Institute, and her colleagues wanted to try a similar type of gradient structure to create a durable, bendable material for soft robots.

The team created this new material by superimposing various microscopic layers of molecules according to the specific chemical gradient of nacre. They developed an elastomeric actuator with sulfonated graphene-based gradient nanostructures that produces a stretchy, flexible material that is tough and can tolerate high temperatures.

From this material, the researchers made robotic fish capable of bending and twisting, and even pulling a weight of up to 5 kg. More importantly, the bionic fish can absorb pieces of microplastics freely floating nearby, because organic dyes, antibiotics, and heavy metals in microplastics have strong chemical bonds and electrostatic interactions with fish materials. In this way, the particles are attracted to the surface of the fish and are then absorbed and removed from the water.

“Once the robot collects the microplastics from the water, the researchers can further analyze the composition and physiological toxicity of the microplastics,” Wang said.

The tiny robot fish is only 15mm long (about half an inch), but it responds to near-infrared laser light by flapping its tail and “swimming” forward. It can move at 2.67 body lengths per second, a speed that is about the same as active phytoplankton moving through water. At this point, the robo-fish only works at the surface of the water, where it would be able to absorb floating microplastics but not those deeper in the water column.

Additionally, the newly developed nanocomposite material from which the robots are made is capable of healing itself, said Wang, who specializes in developing self-healing materials. This means that the robot fish can regain 89% of its previous capacity and continue to absorb pollutants, even if it is damaged or torn, which could happen if it goes in search of microplastics in rocky environments or in choppy waters.

At this point, the robot fish is just a proof of concept, Wang notes, and a lot more research is needed, especially on how this technology could be deployed in the real world. For example, Wang’s team will soon be working on more functionally complex robo-fish that can go below the water’s surface in search of microplastics in the water column. Still, this bionic design could inspire other similar projects, Wang said. “I think nanotechnology holds great promise for trace adsorption, collection and detection of pollutants, improving response efficiency while reducing operating costs.”

By Alison Bosman, Terre.com Personal editor

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